Reaction products of dihydrocarbon dithiophosphoric acid and phosphite



3,338,066 REACTION PRODUCTS OF DIHYDROCAR- EON DITHIOPHGSPHORIC AC1!) AND PHOSPl-HTE Rosemary GHalloran, Union, NJ, assignor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Continuation-impart of application Ser. No. 426,445, Dec. 22, 1964. This application July 26, 1966, Ser. No. 567,847

7 Claims. (til. 252-466) ABSTRACT OF THE DISCLGSURE The reaction product of dihydrocarbon dithiophosphate acid containing 4 to 40 carbon atoms with a phosphite containing 2 to 30 carbon atoms forms an additive for lubricating oil and gasoline.

This application is a continuation-in-part of my earlier application Ser. No. 420,445, entitled, Reaction Product of Dithiophosphoric Acid and Dibasic Acid Anhydride, filed Dec. 22, 1964, and now issued as US. Patent 3,324,032.

This invention relates to reaction products of dihydrocarbon dithiophosphoric acid and phosphite, methods of preparing said reaction products, and the use of said reaction products including their use as additives for lubricants and fuels, and as pesticides. The reaction products of the invention have been found particularly useful as ashless additives for inhibiting oxidation and wear, while imparting loadcarrying ability and other desirable properties, in lubricating oil compositions, such as crankcase and transmission oils, and in fuels such as diesel fuel, gasoline, etc.

Various derivatives of dihydrocarbon dithiophosphoric acid, particularly derivatives of dialkyl dithiophosphoric acid prepared by reacting alcohol with P 8 have long been known as lubricating oil additives. The most common of these additive derivatives are the metal salts, particularly zinc dialkyl dithiophosphate which is in widespread use in lubricating oil because of its excellent antioxidant, antiwear, and load-carrying properties. Recently, the trend is to eliminate ash-forming additives in crankcase lubricating oils to thereby produce ashless lubricants which form less deposits in the combustion chamber than metal-containing, ash-forming lubricants. In view of this trend, a number of attempts have been made to make nonmetallic derivatives of dialkyl dithiophosphoric acids, while retaining the sulfur and phosphorus content, since these latter two elements appear to contribute substantially to the antioxidant, antiwear, and load-carrying functions of the additive. Unfortunately, a number of these nonmetallic ashless dithiophosphoric acid derivatives have various disadvantages. For example, various dialkyl dithiophosphoric acids, which are too corrosive to be used in lubricants per se, have been neutralized with: alkylene oxides, e.g., propylene oxide; alkylene amines, e.g. ethylene diamine; ammonium salts, etc. However, in general, these prior neutralized derivatives are corrosive to the copper-lead bearings that are frequently used in engines. Now, the present invention is based upon the discovery that dihydrocarbon dithiophosphoric acid can be reacted with a dihydrocarbon phosphite, to give an ashless product having good antioxidant, antiwear, and load-carrying properties, while at the same time having a low corrosivity to steel and copper-lead bearings.

3,388,055 Patented June 11, 1968 ice The dihydrocarbon dithiophosphoric acids used in the invention include those of the formula:

ROS

wherein R represents the same or different hydrocarbon radicals of 1 to 30, preferably 2 to 12, carbon atoms each, including radicals such as aryl, alkyl, aralkyl, cycloalkyl radicals, etc. Preferably, R represents alkyl groups, particularly those of 3 to 8 carbon atoms each. Usually, the total number of carbon atoms in both Rs will be about 4 to 40, preferably 6 to 14. Examples of such dihydrocarbon dithiophosphoric acids include diamyl dithiophosphoric acid; lauryl phenyl dithiophosphoric acid; diphenyl dithiophosphoric acid; dicapryl dithiophosphoric acid; dilauryl dithiophosporic acid; amyl-butyl dithiophosphon'c acid; di-C Oxo dithiophosphoric acid; etc.

The phosphites which can be used are those represented by the general formula:

wherein each R is either hydrogen or a hydrocarbon radical which can be branched or straight chain, aliphatic or aromatic, saturated or unsaturated, substituted or unsubstituted, containing 1 to 20, preferably 2 to 8, carbon atoms. At least one R is a hydrocarbon radical. The total number of carbon atoms will generally be about 2 to 30, usually 5 to 15. Examples of such phosphites include monolauryl phosphite, di-n-butyl phosphite; dimethly phosphite; diphenyl phosphite, phenyl phosphite, cyclohexyl phosphite, dicyclohexyl phosphite, methyl phenyl phosphite, etc.

The additives of the invention are made by reacting dihydrocarbon dithiophosphoric acid and phosphite by simply mixing these two reactants and heating for about 1 to 20 hours, usually 3 to 8 hours at temperatures of 150 to 400, referably 200 to 300 F. Equal molar amounts will usually be used, although from .40 to 1.30 moles of phosphite can be used per mole of dithiophosphate.

in my prior patent application Ser. No. 420,445, filed Dec. 22, 1964, it was shown that dibasic acid anhydrides could be reacted with dihydrocarbon dithiophosphoric acid in order to form ashless additives. These dibasic acid anhydrides included aliphatic, aromatic, saturated or unsaturated, substituted or unsubstituted, compounds having 3 to 6 carbon atoms in the ring portion of the anhydride, which ring can be unsubstituted or substituted. Examples of such anhydrides included maleic anhydride, phthalic anhydride, succinic anhydride and alkenyl succinic anhydride wherein the alkenyl groups had 1 to 250 carbon atoms. In the present invention, I have further found that mixtures of the aforesaid phosphites and said dibasic acid anhydrides can be reacted with the dihydrocarbon dithiophosphoric acids. These mixtures can be in any proportion, for example, 0 to mol. percent of said dibasic anhydride and to 10 mol. percent of said phosphite. Generally, a molar amount of the mixtures will be reacted per mole of the dihydrocarbon dithiophosphoric acid. One advantage of these mixtures is that the final product can be adjusted somewhat so as to control the sulfur to phosphorus ratio to achieve optimum results, depending upon the end use of the additive. Generally speaking, a higher sulfur content (less phosphite and more dibasic acid anhydride) will give better extreme pressure and high temltssaoee (3 perature antioxidant properties to the lubricant or fuel, while a higher phosphorus content (more phosphite and less dibasic acid anhydride) will give better anti-wear protection.

Lubricating oil compositions will generally comprise a major proportion of lubricating oil. and 0.01 to .10 wt. percent, preferably 0.1 to wt. percent, of the additive of the invention. Oil concentrates may contain to 80 wt. percent of the additive. For use in fuels, such as gasoline and fuel oil, amounts of about .001 to 1.0 wt. percent of the additive will generally be used.

The oil component of the lubricating oil compositions can be a mineral lubricating oil or a synthetic lubricating oil including diesters such as di-Z-ethylhexyl sebacate, complex esters, carbonate esters, polysilicones, and other synthetic oils.

The lubricating compositions of the invention can also include conventional lubricating oil additives in amounts of 0.05 to 10.0 wt. percent, usually 0.5 to 4.0 wt. percent each, based on the weight of the total composition. For example, oxidation inhibitors such as phenyl-alpha-naphthylamine; rust inhibitors such as over-based sulfonates and alkylamines; detergent additives such as basic calcium petroleum sulfonate, phosphosulfurized polyisobutylene, and barium phenate sulfide; viscosity index improvers and pour depressants such as polymethacrylates; dyes; ashless sludge dispersants, etc. can be used.

The invention will be further understood by reference to the following examples which include a preferred embodiment of the invention and wherein all percents are by weight.

EXAMPLE 1 Equal molar amounts of a dialkyl dithiophosphoric acid and dibutyl phosphite were reacted together as follows: 250 grams of a C /C dialkyl dithiophosphoric acid and 194 grams of dibutyl phosphite, were added and mixed in a 4-neck flask equipped with thermometer. condenser and stirrer, while being heated by a surrounding electric mantle. The reactants were mixed for a total of 4 hours. During the first two hours of mixing, the temperature was raised to 250 E, which temperature was maintained for another two hours. At the end of the fourth hour, the heat was turned otf and the mixture was cooled. When the temperature had dropped to 200 F.. the mixture was blown with nitrogen for 30 minutes to remove any residual H 8 in the mixture. The resulting product was a water-white liquid containing 12.32% sulfur and 13.25% phosphorus, while having a neutralization number of 96 mg. KOH/gm. and a pH of 2.2.

The C /C (isobutyl/amyl) dithiophosphorlc acid used L above, on a weight basis, had about 65% primary amyl groups and about primary isobutyl groups, and was formed by reacting P 8 with a mixture of wt. percent amyl alcohol and 35 wt. percent isobutyl alcohol.

The resulting product was then incorporated into a 10W-30 crankcase motor oil base in an amount sutficient to impart a phosphorus concentration of 0.06 wt. percent, based on weight of the total composition. This l0W-3 motor oil base was a fully formulated ashless automobile motor oil of the 10W-30 type, except that it did not contain the .usual antiwear additive. More specifically, this base consisted of a major amount of neutral distillate mineral lubricating oil, a chlorinated wax-naphthalene pour depressant additive, a high molecular weight polyisobutylene V.I. improving additive, an ashless sludge dispersant made by reacting equal molar proportions of polyisobutenyl succinic anhydride with tetraethylene pentamine and acetic acid, and phosphosulfurized alpha-pinene as an antioxidant.

For comparison, a sample was made up in the same 10W-30 lubricant base using the zinc salt of the aforesaid C /C dialkyl dithiophosphoric acid, also in a phosphorus concentration of 0.06 wt. percent.

The following tests were then carried out:

A Falex Wear Test was made by running the test com- 4. positions in a Falex Wear Test machine for 30 minutes under 500 lbs. direct gauge reading and then determining the milligrams of wear of the steel pin used for the test.

Stability was determined by H 8 evolution after storage for one hour in a closed jar at F. by placing a paper strip soaked with a lead acetate in the top of the closed jar for 5 minutes and then examining the strip for darkening caused by H 5 evolution.

Copper corrosion tests were carried out according to ASTM Dl30 procedure by immersing a copper strip for 3 hours in the composition while at 210 F., and then color rating the strip.

Also. a laboratory multiple-oxidation test was carried out by air blowing at the rate of 10 liters per hour a 40 cc. sample maintained at 300 F., for 5 days, said sample containing a 19" length of #14 gauge copper wire and 2.2 gm. of iron powder as catalysts, in which sample a long sanded A" strip of aluminum is also immersed to detect varnish deposits. At the end of the 5-day period, the sludge was measured by placing a drop of the oxidized oil on a piece of blotting paper and visually observing the amount of sludge separation, if any. The amount of varnish deposited on the aluminum strip was rated visually on a 0 to 5 scale, where 0 denotes no varnish deposits, 1 denotes slight varnish deposits, and 5 denotes very heavy deposits, etc.

Neutralization number was also determined in terms of mg. KOH/ gm. according to ASTM D-974.

In addition, the test compositions were tested for steel corrosion using a copper-lead bearing with a steel backing which was suspended in the test oil, to which lead oxide as a catalyst had been added, for 5 days while at 300 F. Upon removal of the bearing, it was washed in hexane and acetate solvents, and then maintained in a Water saturated atmosphere for 7 days at room temperature.

The results obtained are summarized in Table I which follows:

Cl; gylgOSlOIl, 3 hrs. at G0odtrace red Excellent.

.Lab-Multi-Ox. Test, 5 days at; 300 F..-

Slndge Very light None. Varnish Lt. trace Do. Neut. No. mg. KOH/gm 6.3 3.3.

Steel Corr. 5 days at 300 F.+ No rust Tr. rust. 7 days in Wet atm N o stain N o stain.

As seen by the Falex wear data of the preceding table, the reaction product of the invention, i.e. the product of Example 1, was more effective in reducing wear than the conventional zinc dialkyl dithiophosphate which is currently in widespread commercial use, and was also superior in having a lesser effect towards steel corrosion.

EXAMPLE 2 .47 wt. percent of the additive of Example 1 was dissolved in 99.53 wt. percent of the 10W-30 crankcase motor oil base previously mentioned, and the resulting composition was tested for effectiveness as a crankcase lubricating oil in the MS. Sequence I Test in an Oldsmobile automobile engine. Before testing, the cams and valve lift lBIS from the engine were measured and then placed in the engine. After the test period, the cams and valve lifters were again measured and the average cam and lifter wear was determined. For comparison, the W-30 motor oil base per se, and 98.8 wt. percent of the 10W-30 motor oil base containing 1.2 wt. percent of an 85 wt. percent concentrate of the aforementioned zinc C /C dithiophosphate in mineral lubricating oil, were run in similar tests.

The results of the above M.S. Sequence Test are summarized in the following Table II:

TAB LE II M.S. Sequence I Test Combined cam and litter wear X10- inches Additive None (base oil blend per se ex-outwear agent) 1 50 +1037 wt. percent product of Example 1 (.06 wt. percent P) 14 +1.2 wt. percent of 85 wt. percent concentrate zinc (li-C4/C5 dithiophosphate 22 1 Aver. 2 runs.

Several additives were made up following the procedure of Example 1, but in which different molar ratios of the phosphite and dihydrocarbon dithiophosphoric acid Were used. The additives made and their main properties are summarized in Table III which follows:

TAB LE III Mole ratio of phosphite to dithiophosphoric acid Wt. Percent Phosphorus \Vt. Percent Sulfur 10.34 12.32 12. 54 14.18 Falex Wear Test: min./50O lbs, (mg.

1 Falex Wear Test carried out at a .06 wt. percent P concentration in the previously described motor 011 base.

EXAMPLE 4 As mentioned previously, mixtures of the phosphite along with an anhydride can be reacted with the dithiophosphoric acid so as to adjust the sulfur and phosphorus content of the final product. A series of additives were made in this way following the general procedure of Example 1. The products prepared and their properties are summarized in Table IV which follows:

the common housefly, Musca domestica, and was effective as a pesticide. Fungicide tests were carried out using concentrations of 0.1 and .01 wt. percent of said reaction product in acetone by applying it to Mom'lia fructicola, the causal organism of brown rot of stone fruit, and Alternaria alteracea, the causal organism of early blight of potato and tomato. The reaction product of Example 1 was effective in inhibiting spore germination of both organisms at both concentrations. The reaction product of Example 1 was diluted to a 6 wt. percent concentration in acetone, which concentration was next diluted with water to give a final concentration of .01 wt. percent of said reaction product. This .01% concentration was effective on a species of Panagrellus which was used as the test organism, thereby demonstrating its use as a nematocide.

For use as pesticides, the reaction products of the invention can be dissolved in liquid hydrocarbon solvents, such as kerosene, as a carrier for application.

As a further illustration of the invention, the reaction product of Example 1 can be added to gasoline as an antioxidant at a .01 wt. percent concentration.

What is claimed is:

1. A composition comprising a major amount of a material selected from the group consisting of lubricating oil and gasoline, and about .001 to 10 wt. percent, based on the weight of said composition, of a reaction product of a dihydrocarbon dithiophosphoric acid containing a total of 4 to 40 carbon atoms and a phosphite of the formula:

wherein R is selected from the group consisting of hydrogen and hydrocarbon radicals of 1 to 20 carbon atoms, and the total number of carbon atoms in said phosphite is about 2 to 30, wherein said reaction product is prepared by heating about .4 to 1.3 molar proportions of said phosphite per molar proportion of said dithiophosphoric acid at about 150 to 400 F. for about 1 to 20 hours.

2. A composition according to claim 1, wherein said material is mineral lubricating oil, the amount of said reaction product is about 0.1 to 10 wt. percent, said dithiophosphoric acid is a dialkyl dithiophosphoric acid having 3 to 8 carbons in each alkyl group and totaling about 6 to 14 carbons, said phosphite is dibutyl phosphite, and said dithiophosphon'c acid and said phosphite are heated together in substantially equal molar amounts at 200 to 300 F. for about 3 to 8 hours.

TABLE IV Charge in mol. percent Sol. Ratio P, S, 04/0 dithio- Maleic Dibutyl in Oil, Color pH S/P wt. wt. Odor phosphoric acid Anhydride Phosphite percent percent percent 50 0 Nil 1. 69 8. 6 14. 5 Bad. 40 0 1 1. 36 10. 3 14. 0 38 38 25 3 1. 24 10. 4 12. 9 Fair. 38 50 12 1 1. 42 9. 5 13. 5 D0. 43 43 14 I 1. 51 9. 6 14. 5 D0.

As seen by Table IV, the P and S ratio of the reaction product, i.e. the additive, can be varied by replacing some of the phosphite with anhydride.

EXAMPLE 5 The reaction product of Example 1, made by the reaction of equi-molar amounts of dibutyl phosphite and the C /C dialkyl dithiophosphoric acid was tested for pesticide activity and found effective as an insecticide against housefiies, as a fungicide and as a nematocide. Thus, two microliters of a solution consisting of 0.5 wt. percent of said reaction product dissolved in acetone, was applied topically to the thorax of a non-resistant strain of 3. A composition according to claim 1, wherein said material is mineral lubricating oil, the amount of said reaction product is about 0.1 to 10 wt. percent, said dihydrocarbon dithiophosphoric acid is dialkyl dithiophosphoric acid having 2 to 12 carbon atoms in each of said alkyl groups, and wherein said phosphite is a secondary phosphite wherein R represents alkyl groups containing 2 to 8 carbon atoms.

4. A composition according to claim 3, wherein each of said dialkyl groups of said dialkyl dithiophosphoric acid contains 3 to 8 carbon atoms.

5. A method of preparing a reaction product of a dilil,388,066

l7 hydrocarbon dithiophosphoric acid containing a total of 4 to 40 carbon atoms and a phosphite of the formula:

wherein R is selected from the group consisting of hydrogen and hydrocarbon radicals of 1 to 20 carbon atoms. and the total number of carbon atoms in said phosphite is about 2 to 30. comprising heating said dithiophosphoric acid with said phosphite at a temperature in the range of about 150 to 400 F. for about 1 to 20 hours, in a molar ratio of about .4 to 1.3 molar proportions of said phosphite per molar proportion of said dithiophosphoric acid.

6. A methd according to claim 5. wherein said dithio- 15 phosphoric acid is a dialkyl dithiophosphoric acid having 3 to 8 carbon atoms per alkyl group, and both R"s are C; to C hydrocarbon radicals.

7. A method according to claim 6, wherein substantially equal molar ratios of said acid and said phosphite are reacted by heating at about 200 to 300 F. for about 3 to 18 hours.

References Cited lJNITED STATES PATENTS 3.443.264 l5/1948 Mikeska 252-46.6 2,567,154 9/1951 Kosolapolf 25246.6 XR 2.582.204 l/1952 Kosolapoff 167-22 2,66 .722 12/1953 Toy 1672Z XR I3,l6l,487 l2/1964 Giammaria et a1 44-69 3.324.032 l/1967 OHalloran 25246.6

iDANIEL E. WYMAN, Primary Examiner.

W. H. CANNON, Assistant Examiner. 

